sin(a+b)/cosa*cosb=tga+tgb;
sin(a+b)/cosa*cosb=sinacosb+cosasinb/cosa*cosb=cosa(tga*cosb+sinb)/cosa*cosb=tga*cosb+sinb/cosb=cosb(tga+tgb)/cosb=tga+tgb.
tga+tgb=tga+tgb. - Доказано!
sin(a+b)/cosa*cosb=tga+tgb;
sin(a+b)/cosa*cosb=sinacosb+cosasinb/cosa*cosb=cosa(tga*cosb+sinb)/cosa*cosb=tga*cosb+sinb/cosb=cosb(tga+tgb)/cosb=tga+tgb.
tga+tgb=tga+tgb. - Доказано!